Here's what I found for 1970 on a Mopar tech site:
Differential Options:
• Low Performance models came standard with a 7.25 inch housing with either 2.76:1 or 3.23:1 ratio gearing.
• High Performance models came standard with a 8.75 inch housing with 2.76:1, 3.23 :1, 3.55:1, and 3.91:1 ratios, and an option of "SureGrip" limited slip. The 3.23 and 3.55 were the most common, with the 3.55:1 being standard in the T/A with an optional 3.91:1.
• Hemi models with a manual transmission came with a 9.75 inch Dana 60 "SureGrip" axle standard offering either 3.54:1 or 4.10:1 gearing, and in 440 and Hemi automatic models, this rear differential was optional, in place of the 8.75 housing.
P.G.